Colors can be represented, as described in JISZ8701 "METHOD OF REPRESENTING COLORS BY TWO DIMENSIONAL FIELD XYZ SYSTEM," by numerical values of x, y and Y. However, although color can be numerically represented by this method, it is quite difficult to understand what color is meant by these numerical values.
Conventionally, a chromaticity chart consisting of x-y coordinates has been used to enable a prompt understanding of the nature of the color cited. Paper strips of colors corresponding to the x and y values of these coordinate points are attached to a number of coordinate points on the chart. In order to appreciate the nature of a color reference, the x and y values of the color cited are manually located on the chromaticity chart, and the subject color can be judged from the color of the paper strip attached to the located coordinate point or estimated from the colors of the paper strips around the located point.